Topic overview

Start with the big picture

Skeletal muscle responds to stimulation with an action potential, conducts that signal through the fiber, and uses actin–myosin interactions to develop force. Elastic structures help restore length after stretch. A single fiber follows an all-or-none response, while whole-muscle force can be graded through motor-unit recruitment and firing rate. Force also depends on muscle length and shortening speed, and contractions may occur with or without a change in muscle length. The lesson places these mechanics alongside twitch summation, recruitment order, fiber types, energy systems, fatigue, sensory feedback, and adaptation to loading or unloading. Together, these ideas provide a framework for understanding how skeletal muscle responds to demands and changes over time.